Skip to main content
ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Produce Safety and Microbiology Research » Research » Publications at this Location » Publication #422695
Research Project: Elucidating the Factors that Determine the Ecology of Human Pathogens in Foods

Location: Produce Safety and Microbiology Research

Title: A new bacteriophage cocktail with enhanced mitigating effects reduces Shiga toxin-producing Escherichia coli O157:H7 in agriculture water, mung beans, and biofilm

Author
item Liao, Yen-Te
item Zhang, Yujie
item Salvador, Alexandra
item Campos, David
item HO, KAN-JU - Forest Service (FS)
item Wu, Vivian

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/5/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: N/A

Technical Abstract: Shiga toxin-producing E. coli (STEC) O157:H7 is one of the most notorious foodborne pathogens, posing a risk to public health and economic loss. Due to the rising issue of antimicrobial resistance and reoccurring pathogen contamination, developing innovative antimicrobial interventions, such as lytic bacteriophages, is necessary. Therefore, the objective was to formulate a lytic phage cocktail from the environmentally isolated phages with enhanced activity upon application to mitigate E. coli O157:H7 strains. Three genetically different phages, with morphologies belonging to the families Myoviridae (G157lw and Sa157lw) and Siphoviridae (Elw), were isolated from environmental samples, such as non-fecal compost, surface water, and sewage water. The toxin or lysogeny-associated genes were absent in the phage genome. Biological characterization was conducted, including the one-step growth curve, host range, and stability tests. Subsequently, the in vitro antimicrobial activity tests of different phage combinations were conducted for cocktail formulation. The most effective phage combination was applied to surface water, mung bean seeds, and biofilm to reduce E. coli O157:H7 contamination. G157lw had the largest burst size (1220 PFU/CFU) and showed lytic infection against multiple serogroups (O157, O45, O103, and O145) of STEC, whereas the other two phages only infected STEC O157. Moreover, phages Elw and G157lw showed infection against generic E. coli ATCC13706, while Sa157lw could target Salmonella enterica strains. The in vitro antimicrobial activity results showed that the three-phage combination expressed a stronger antimicrobial effect against E. coli O157:H7 than any of the two-phage combinations, contributing to more than 6 log reduction after 24-h phage treatment at 25°C. Upon application, the three-phage cocktail reduced a four-strain E. coli O157:H7 cocktail on the contaminated mung beans by 1 log after phage treatment for 1 hour and the same bacterial cocktail spiked in an agricultural water by 0.8 log. Furthermore, the phage cocktail dispersed 48-h E. coli O157:H7 biofilm on a stainless surface by more than 2 log after phage treatment (8 log PFU/mL) for 1 hour at 22°C. Most importantly, this phage cocktail also showed stronger antimicrobial effects than a commercial phage product among all applications. The findings indicate the potential of the three-phage cocktail for developing enhanced biocontrol agents in mitigating E. coli O157:H7 strains on food or food-associated environments to improve food safety.